Esophageal pacing: a diagnostic and therapeutic tool.

The purpose of this study was to develop guidelines for reproducible esophageal pacing of the atria and to determine the incidence of successful initiation and termination of tachycardia using this technique in patients with a history of spontaneous supraventricular tachycardia (SVT). Strength-duration curves were performed in 39 patients using a bipolar esophageal lead with a 2.9-cm interelectrode distance. Unlike strength-duration curves normally obtained -in cardiac tissue, which plateau at pulse durations more than 2.0 msec, the esophageal current threshold decreased progressively as pulse duration was increased to the limit of the stimulator (9.9 msec). At pulse durations of 8.0-9.9 msec, atrial capture was achieved in all patients. At progressively shorter pulse durations, capture was achieved in progressively fewer patients despite use of current up to 30 mA. Stable pacing was achieved in 26 of 39 patients with a pulse duration of 1.0 msec (mean threshold 21 mA), in 33 of39 patients with a pulse duration of 2.0 msec (mean threshold 18 mA), and in 39 of 39 patients with a pulse duration of 9.9 msec (mean threshold 11 mA). The current requirements did not correlate with the amplitude of the unipolar or bipolar atrial electrogram recorded in the